Fine cobalt metal powder has been produced by converting cobalt chloride to either pentammine cobalt chloride or hexammine cobalt (III) chloride and thereafter converting these ammine complexes to cobaltic hydroxide which is then reduced to the metal. Disadvantages of these processes are high chemical costs associated with the use of relatively expensive ammonia which is used in the oxidation and subsequent acidification used in purification. Also, relatively large amounts of sodium hydroxide are required to neutralize the solution to precipitate cobaltic hydroxide.
Therefore a process which overcomes the above disadvantages would be desirable.
The following U.S. Patents relate to cobalt processing:
U.S. Pat. No. 4,184,868 relates to a method for producing extra fine cobalt metal powder by digesting cobalt pentammine chloride in ammonium hydroxide to obtain a black precipitate which contains cobalt and which is thereafter reduced to metal powder. U.S. Pat. No. 4,214,894, 4,233,063, and 4,278,463 relate to improvements in U.S. Pat. No. 4,184,868 in which the ammonia solutions are processed to recover any cobalt therein. U.S. Pat. No. 4,395,278 and 4,469,505 relate to improvements in U.S. Pat. No. 4,184,868 in which fine cobalt metal powder is produced having reduced tailings.
U.S. Pat. No. 4,214,895 relates to a process for producing cobalt metal powder which involves treating an aqueous solution of a soluble cobaltic ammine halide with a sufficient amount of a soluble metallic hydroxide to form a cobalt containing precipitate which is thereafter reduced to metallic cobalt.
U.S. Pat. No. 4,218,240 relates to a method for producing cobalt metal powder by forming a solution of a cobalt hexammine compound and treating the solution with a metallic hydroxide to form a precipitate which is reduced to cobalt metal powder. U.S. Pat. Nos. 4,348,224 and 4,381,937 relate to improvements in the process described in U.S. Pat. No. 4,218,240 which involve removal of copper and silver from the cobalt. U.S. Pat. No. 4,452,633 relates to an improvement in the processes described in U.S. Pat. Nos. 4,218,240 and 4,348,224 in which the silver is recovered.
U.S. Pat. No. 4,093,450 to Doyle et al describes a process for producing fine particle size cobalt metal powder by the hydrogen reduction of cobalt oxide obtained from a cobalt pentammine carbonate solution. The precipitate is formed by heating the solution to drive off ammonia and carbon dioxide to form a precipitate of cobalt oxide.
U.S. Pat. No. 4,329,169 relates to a process for producing fine cobalt metal powder absent tailings by heating an aqueous solution of soluble cobalt ammine halide to decompose the halide and form a cobalt containing precipitate which is reduced to the cobalt metal powder.
U.S. Pat. No. 4,409,019 relates to a process for producing fine cobalt metal powder from pieces of relatively pure cobalt by dissolving the cobalt pieces in an aqueous solution of hydrogen iodide and iodine and forming a cobalt containing solid which is subsequently reduced to a fine cobalt metal powder.